A fastener is a type of mechanical accessory used for fastening and connection and is widely applied. Various fasteners are used in machineries, devices, vehicles, ships, railways, bridges, buildings, structures, tools, instruments, meters, articles for use, and the like. A type of fastener with a national standard is referred to as a standard fastener, or referred to as a standard part for short. The fastener is the most widely used basic mechanical accessory.
The fastener generally includes the following 13 types of accessories: a bolt, a stud, a screw, a nut, a self-tapping screw, a wood screw, a washer, a ring, a pin, a rivet, an assembly and a bolt, a welded screw, and a wire thread insert. The washer is a fastener shaped like an oblate ring, and is placed between a supporting plane of a bolt, a screw, or a nut and a surface of a connection accessory, so as to enlarge a contact surface area of a connected accessory, reduce unit area pressure, and protect a surface of the connected accessory from being damaged. Another elastic washer is further capable of preventing the nut from loosening.
During fastening, the fastener needs to be fastened according to a specified or required torque. An improper tightening torque loosens and invalidates the screw, causing a relatively high security risk and a relatively severe potential quality threat. Currently, a common method on the market is to use an additional professional torque tool such as a torque batch, a torque wrench, or a torque socket for fastening, so as to ensure a tightening torque.
At present, the torque tool is much more expensive than a common tool, and some Japanese products with a higher requirement are more expensive, increasing production investment. In addition, for fastening by using a tool, a professional person needs to adjust torques specific to different screw models, and a common operator is prone to an incorrect operation, causing a quality threat.